Handheld driving devices comprising propellant charges are known from the prior art; in such devices the resulting combustion gases, following the ignition of a pyrotechnic charge, expand in a combustion chamber. Thereby a piston as an energy transmission means is accelerated and drives a fastening means into a workpiece. An optimized, residue-free and reproducible combustion of the charge is fundamentally desired. It must be considered in this regard that the charge generally comprises powder grains, fibers or the like, which are initially driven ahead of a flame front following an ignition.
U.S. Pat. No. 6,321,968 B1 describes a driving device having a propellant charge, in which the combustion chamber is separated by means of a perforated sieve into an upper partial chamber and a lower partial chamber. Before combustion, the powder grains are larger than the holes of the sieve. Therefore, unburnt powder grains are initially accelerated in a central discharge region toward the perforated regions of the separating disc, where they are held back due to the dimensioning of the holes in the separating disc such that the powder grains are largely combusted in the upper partial chamber. FIG. 10 shows a variation in which a propellant charge without a cartridge is used. Based on the design in this variant, a discharge region enclosing the central axis in the upper partial chamber and extending between the propellant charge and a central region of the separation disc is not provided. The discharge region in the example according to FIG. 10 is arranged in an annular manner about a central plunger of the combustion chamber. The cartridge-free charge is ignited at an upper end of the central plunger.
The problem addressed by the invention is that of specifying a driving device that enables a uniform and optimally complete combustion of a pyrotechnic propellant charge.